Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Protheroe, Clare Louise; Ravensbergen, H. J. C.; Inskip, Jessica A.; Claydon, Victoria E.

doi:10.3791/4315-v

Cited by 3 publications

(3 citation statements)

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“…A more accurate method of measuring PV, e.g., using a dye dilution method or radioactive tracer (46) may have demonstrated this and indeed PV has been shown to be positively correlated to OT in previous studies (47). These data point to the ways in which HA may protect CO when baroreceptor regulated responses would otherwise be overwhelmed by heat stress (48) and therefore reduce the risks of syncope, co-incident with improving performance capacity relative to initial heat exposure (32) (33) (34–36).…”

Section: Discussionmentioning

confidence: 97%

“…Orthostatic tolerance was measured using HUT/ LBNP. Others have previously shown this technique to be reproducible and reliable for examining the effects of interventions aimed at improving OT (20,34,35). Participants rested in the supine position on the tilt table for 15 min to assess baseline cardiovascular parameters.…”

Section: Preexposure and Postexposure Testingmentioning

confidence: 99%

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Improvements in Orthostatic Tolerance with Exercise Are Augmented by Heat Acclimation: A Randomised Controlled Trial

Parsons,

Snape,

Stacey

et al. 2023

Medicine &Amp; Science in Sports &Amp; Exercise

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Introduction Heat adaptation is protective against heat illness however its role in heat syncope, due to reflex mechanisms, has not been conclusively established. The aim of this study was to evaluate if heat acclimation (HA) was protective against heat syncope and to ascertain underlying physiological mechanisms. Methods 20 (15 males, 5 females) endurance trained athletes were randomised to either 8 days of mixed active and passive HA (HEAT) or climatically temperate exercise (CONTROL). Prior to, and following, the interventions participants underwent a head up tilt (HUT) with graded lower body negative pressure (LBNP), in a thermal chamber (32.0 ± 0.3 °C), continued until presyncope with measurement of cardiovascular parameters. Heat stress tests (HST) were performed to determine physiological and perceptual measures of HA. Results There was a significant increase in orthostatic tolerance (OT), as measured by HUT/LBNP, in the HEAT group (pre-intervention; 28 ± 9 mins, post-intervention; 40 ± 7 mins) compared to CONTROL (pre-intervention; 30 ± 8 mins, post-intervention; 33 ± 5 mins) (p = 0.01). HA resulted in a significantly reduced peak and mean rectal and skin temperature (p < 0.01), peak heat rate (p < 0.003), thermal comfort (p < 0.04) and rating of perceived exertion (p < 0.02) during HST. There was a significantly increased plasma volume (PV) in the HEAT group in comparison to CONTROL (p = 0.03). Conclusions HA causes improvements in OT and is likely to be beneficial in patients with heat exacerbated reflex syncope. HA mediated PV expansion is a potential physiological mechanism underlying improved OT.

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Section: Discussionmentioning

confidence: 97%

Section: Preexposure and Postexposure Testingmentioning

confidence: 99%

Improvements in Orthostatic Tolerance with Exercise Are Augmented by Heat Acclimation: A Randomised Controlled Trial

Parsons,

Snape,

Stacey

et al. 2023

Medicine &Amp; Science in Sports &Amp; Exercise

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show abstract

“…1. Each participant underwent three head-up tilt (HUT) tests with graded lower body negative pressure continued until presyncope, following our standard procedure [16]. Prior to HUT, participants were supine for two 15-minute periods.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of stroke volume estimation during orthostatic stress: the utility of Modelflow

Lucci,

Parsons,

Hockin

et al. 2023

Blood Pressure Monitoring

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Advanced blood pressure monitoring devices contain algorithms that permit estimation of stroke volume (SV). Modelflow (Finapres Medical Systems) is one common method to non-invasively estimate beat-to-beat SV. However, Modelflow accuracy during profound reductions in SV is unclear. We aimed to compare SV estimation by Modelflow and echocardiography, at rest and during orthostatic challenge. We tested 13 individuals (age 24 ± 2 years; 7 female) using combined head-up tilt and graded lower body negative pressure, continued until presyncope. SV was derived by both Modelflow and echocardiography on multiple occasions while supine, during orthostatic stress, and at presyncope. SV index (SVI) was determined by normalising SV for body surface area. Bias and limits of agreement were determined using Bland-Altman analyses. Two one-sided tests (TOST) examined equivalency. Across all timepoints, Modelflow estimates of SV (73.2 ± 1.6 ml) were strongly correlated with echocardiography estimates (66.1 ± 1.3 ml) (r = 0.56, P < 0.001) with a bias of +7.1 ± 21.1 ml. Bias across all timepoints was further improved when SV was indexed (+3.6 ± 12.0 ml.m-2). Likewise, when assessing responses relative to baseline, Modelflow estimates of SV (−23.4 ± 1.4%) were strongly correlated with echocardiography estimates (−19.2 ± 1.3%) (r = 0.76, P < 0.001), with minimal bias (−4.2 ± 13.1%). TOST testing revealed equivalency to within 15% of the clinical standard for SV and SVI, both expressed as absolute values and relative to baseline. Modelflow can be used to track changes in SV during profound orthostatic stress, with accuracy enhanced with correction relative to baseline values or body size. These data support the use of Modelflow estimates of SV for autonomic function testing.

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Pain associated with intravascular instrumentation reduces orthostatic tolerance and predisposes to vasovagal reactions in healthy young adults without needle phobia: a randomised controlled study

Hockin,

Lucci,

et al. 2023

Clin Auton Res

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Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Cited by 3 publications

References 0 publications

Improvements in Orthostatic Tolerance with Exercise Are Augmented by Heat Acclimation: A Randomised Controlled Trial

Improvements in Orthostatic Tolerance with Exercise Are Augmented by Heat Acclimation: A Randomised Controlled Trial

Evaluation of stroke volume estimation during orthostatic stress: the utility of Modelflow

Pain associated with intravascular instrumentation reduces orthostatic tolerance and predisposes to vasovagal reactions in healthy young adults without needle phobia: a randomised controlled study

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